The invention relates to an extractor for substances containing a liquid.
The extraction of liquids from certain vegetable substances, such as grapes, has hitherto been carried out using vertical presses of the screw or hydraulic type, or horizontal presses of the type with compression by means of an inflatable diaphragm or with compression by means of opposing circular platens, displacement being provided by cylinders or screws.
On vertical presses, each extraction cycle is followed by a manual breaking-up operation using shovels and forks.
On pneumatic horizontal presses, the breaking-up operation is performed mechanically, by rotation of the cage, after decompression of the diaphragm.
On horizontal presses with compression by means of opposing circular platens, this operation is carried out by rotation of the cage together with retraction of the platens, which, in order to make the mixing process more efficient, are in some cases joined by rings and chains.
Although mechanization of the breaking-up operation has dispensed with laborious manual interventions, it has introduced crushing and grinding processes which impair quality (sludge and turbidity)
A press is already known which is disclosed as prior art in West German Pat. No. 2945254; it is a pneumatic press with a vat rotating about a longitudinal and horizontal axis, which has a filling and emptying aperture and is closed by a filter cover, while a compression diaphragm, similar in shape to the vat and arranged coaxially to the axis of rotation of the vat, is mounted inside the vat, the said diaphragm thus dividing the vat into a pressure chamber and an extraction chamber. This extractor has the advantage of exerting a uniformly distributed pressure on the substance, resulting in a gentle pressing at low pressure. This design is also suitable for a preliminary extraction by centrifugation, the vat being rotated several times without the use of pressure. The extraction operation takes place after a 180.degree. rotation of the vat, which brings the filling aperture, equipped with a filter, to the bottom position; however, when the press-cake is broken up, it is necessary to decompress the diaphragm and then rotate the vat, causing the substance to be mixed and leaving a relatively high level of sludge and turbidity.